"Profiles in History" boss Joe Maddalena recently announced that Armstrong's personal letters would be up for grabs at the event, billed as "Drama, Action, Romance -- The Hollywood Auction," on Dec. 15 and 16, alongside correspondence from John Lennon, Cole Porter and composer Peter Ilyich Tchaikovsky, and now it's clear the "What a Wonderful World" hit-maker's items are a treasure trove of secret notes.

A spokesperson for the auction house says, "They are dated from 1946 to 1968. The collection includes personal letters and postcards, written to Lucille 'Sweets' Preston and Sharon, Armstrong's only biological child.

"Armstrong was friends with Preston and her husband, entertainer Luther 'Slim' Preston, who passed away in 1950. Soon after, Armstrong and Lucille began a relationship, and their daughter, Sharon, was born in 1954. The relationship continued until Armstrong's death in 1971. Armstrong's wife, also named Lucille, never publicly acknowledged Sharon's existence.

The items going on the auction block also include an original private audio reel, featuring a recording from 1959 when Armstrong was in Berlin. On the tape, Armstrong sings "Uncle Satchmo's Lullaby" with 12-year-old German singer Gabriele.